The use of aqueous dispersions of phenolic resole resins as binders in the production of wool and board products made from glass and other vitreous fibers is common place. It has been suggested that urea can be mixed with, but not appreciably reacted, with the phenolic resoles and that the resulting mixtures are useful in the production of wools and boards from glass fibers and other vitreous fibers. The addition of the urea serves several purposes. U.S. Pat. No. 4,255,485 assigned to the assignee of the present invention and incorporated by reference herein, discloses that urea is added to a phenol-formaldehyde condensate in an amount sufficient to scavenge free formaldehyde. See also U.S. Pat. No. 4,956,409 also assigned to the assignee of this invention and incorporated by reference herein, which likewise teaches that it is advantageous to mix urea with phenolic resole resins for use in making products from glass fibers.
In the manufacture of phenolic resole resins, with or without urea modification, it is highly desirable to provide a process for manufacturing the resole resin where the amount of free phenol and formaldehyde remaining after the reaction is held to a minimum. As noted, U.S. Pat. No. 4,255,485 discloses that urea, when added to the phenolic resole resin, reduces the amount of free formaldehyde by reacting with the formaldehyde. To accomplish the objective of low emissions the mol ratio of formaldehyde to phenol is kept above 1. Typical ratios are from about 2 about 4.5. In this way, the amount of free phenol is maintained at a low level.
In preparing phenolic resole resins the catalysts of choice have been the hydroxides of alkali or alkaline-earth metals such as sodium, potassium, calcium and barium hydroxides. The conventional wisdom within the field has been to use about 5 to 8.5% by weight of such a catalyst, based on the weight of phenol used, so that the formation of undesirable insoluble salts are not formed during the subsequent neutralization of the base catalyst with acids such as sulfuric acid. See for example U.S. Pat. Nos. 4,663,419, 4,956,409, and 4,904,516. Some prior patents discuss the need to remove the undesired salt formed during the neutralization reaction. See for example the '409 and '516 Patents just described and U.S. Pat. No. 4,710,406 that discloses in Example 7 that 14.5% by mole of the basic catalyst based on the weight of phenol will produce an unsatisfactory resin.